1. Field of the Invention
The present invention is generally related to a throttle position control method and, more particularly, to a method for controlling the throttle position as a function of both a manually provided throttle demand signal and the air velocity flowing through a throttle body region.
2. Description of the Prior Art
Many different types of engine control methods are well known to those skilled in the art. It is common to use a microprocessor, as an engine control unit, in order to control the engine as a function of various monitored parameters, such as manifold pressure, barometric pressure, and temperature.
U.S. Pat. No. 6,298,824, which issued to Suhre on Oct. 9, 2001, discloses an engine control system using an air and fuel control strategy based on torque demand. The control system for a fuel injected engine provides an engine control unit that receives signals from a throttle handle that is manually manipulated by an operator of a marine vessel. The engine control unit also measures engine speed and various other parameters, such as manifold absolute pressure, temperature, barometric pressure, and throttle position. The engine control unit controls the timing of fuel injectors and the injection system and also controls the position of a throttle plate. No direct connection is provided between a manually manipulated throttle handle and the throttle plate. All operating parameters are either calculated as a function of ambient conditions or determined by selecting parameters by matrices which allow the engine control unit to set the operating parameters as a function of engine speed and torque demand as represented by the position of the throttle handle.
U.S. Pat. No. 6,250,292, which issued to Suhre on Jun. 26, 2001, discloses a method of controlling an engine with a pseudo throttle position sensor value. In the event that the throttle sensor fails, a method is provided which allows a pseudo throttle position sensor value to be calculated as a function of volumetric efficiency, pressure, volume, temperature, and the ideal gas constant. This is accomplished by first determining an air per cylinder (APC) value and then calculating the mass air flow into the engine as a function of the air per cylinder value. The mass air flow is then used, as a ratio of the maximum air flow at maximum power at sea level for the engine, to calculate a pseudo throttle position sensor value. That pseudo throttle position sensor value is then used to select an air/fuel target ratio that allows the control system to calculate the fuel per cycle (FPC) for the engine.
U.S. Pat. No. 5,848,582, which issued to Ehlers et al on Dec. 15, 1998, discloses an internal combustion engine with barometric pressure related start of air compensation for a fuel injector. A control system for a fuel injector system for an internal combustion engine is provided with a method by which the magnitude of the start of air point for the injector system is modified according to the barometric pressure measured in a region surrounding the engine. This offset, or modification, of the start of air point adjusts the timing of the fuel injector system to suit different altitudes at which the engine may be operating.
U.S. patent application Ser. No. 09/882,700 which was filed on Jun. 15, 2001, by Suhre et al, discloses a method and apparatus for determining the air charge mass for an internal combustion engine. The engine and apparatus are provided for calculating the air charge mass for an engine as a function of four measured parameters. These parameters include the engine speed measured by a tachometer, a throttle position measured by a throttle position sensor, a manifold air temperature, and a barometric pressure. Without the need for a mass air flow sensor or a manifold absolute pressure sensor, the present invention provides a system for quickly and accurately calculating the air charge mass for the engine.
U.S. Pat. No. 6,119,653, which issued to Morikami on Sep. 19, 2000, describes an engine running control apparatus for an outboard motor. The apparatus includes a full-closure state detecting device for outputting a full-closure detection signal when the throttle valve is in the fully closed state, a control device for controlling the open degree of the air control valve, a time-measuring device for counting up to a predetermined period of time in response to the full-closure detection signal, an air speed detecting device for detecting the rotating speed of the engine and an initial value setting device for setting up an engine speed at which control of the degree of the opening is started by the control valve, in response to a full-closure detection signal. In this configuration, the control device, in response to the reception of the full-closure detecting signal, fixes the opening of the air control valve until the time-measuring device counts up to a predetermined period of time, and controls the opening of the air control valve after the elapse of the predetermined time so that the engine speed will be reduced at a predetermined rate over time.
U.S. Pat. No. 5,040,505, which issued to Toyoda on Aug. 20, 1991, describes an intaking rate control device of internal combustion engine. The method and apparatus for controlling the air intake rate of an internal combustion engine, including a deceleration control system responsive to actuation of an idle switch during deceleration for bypassing an intake throttle valve and feeding bypass air into the engine is disclosed. The control device actuates the deceleration control system only when the cooling water temperature of the engine is greater than or equal to a predetermined water temperature, the engine is decelerating, the engine speed is less than or equal to an actuation speed associated with the deceleration control system, and the engine speed is changing at a rate which is greater than or equal to an actuation differential change rate associated with the deceleration control system. The control device applies to the deceleration control system a control signal having a duty ratio which corresponds to the change rate of the engine speed and which increases the rate at which bypass air is taken into the engine.
U.S. Pat. No. 5,239,966, which issued to Yamagata et al on Aug. 31, 1993, describes an electronic control fuel injection apparatus for two cycle engine. The fuel injection apparatus for a crank chamber compression type 2-cycle engine which compensates a fuel injection amount predetermined by an opening degree of an engine intake air system and an engine speed in response to a fuel amount reduction rate allocated by using an opening degree of the engine intake air system and an engine speed if the engine speed enters an acceleration loss region during a predetermined deceleration and or re-acceleration of the engine while a deceleration of the engine is detected.
U.S. Pat. No. 4,524,744, which issued to Adams on Jun. 25, 1985, describes a fuel system for a combustion engine. A fuel injection apparatus in which a closed fuel circuit is pressurized, and the amount of fuel injected is determined by the pressure in the circuit. Air intake by the engine is controlled in response to the amount of fuel injected. The fuel injection apparatus includes a reservoir with a fixed level of fuel, and a high pressure pump pumps fuel from the reservoir and into the fuel circuit. Fixed orifice injection nozzles communicate with the circuit so fuel is varied only by the pressure. Pressure in the circuit is varied by a valve that releases fuel into the reservoir to lower the pressure in the circuit, the valve being controlled by the conventional accelerator pedal. Air to the engine is modulated in response to fuel flow. This is accomplished by varying an air valve in accordance with pressure in the fuel circuit, or by using a constant velocity valve which would vary the engine demand. The apparatus further includes an auxiliary chamber receivable in the spark plug hole to convert the engine to a stratified charge engine. The fuel is injected into the auxiliary chamber, and passes from the auxiliary chamber into the cylinder so the cylinder receives a lean mixture. The auxiliary chamber includes a spark plug to ignite the rich mixture, and the chamber acts as a torch to ignite the lean mixture in the cylinder.
U.S. Pat. No. 4,574,760, which issued to Jones et al on Mar. 11, 1986, describes a fuel injection throttle body. A fuel injection system of the single point, throttle body type in which a fuel injector is located centrally above the inlet to an air throttling body that contains a variable venturi consisting of a plug and nozzle assembly wherein the plug includes a fuel dispersion plate directing the fuel towards a movable nozzle together defining a convergent-divergent flow air that is variable in area in response to the dynamic pressure of the air against it at higher air flows or alternately responsive to the suction of the engine at low air flows to be moved to a position providing essentially a constant air velocity flowing past the fuel under all conditions of operation to shear the fuel and thereby atomize the same for an economical and efficient operation of the engine.
U.S. Pat. No. 5,707,560, which issued to Nevin on Jan. 13, 1998, describes a constant velocity carburetor with variable venturi slide having bleed holes at an oblique angle and method of operation. A variable Venturi slide includes a beveled edge at an oblique angle to lower surface of the slide and air flow, and an auxiliary hole having an opening on the beveled edge communicating between the air flow and the interior of the variable Venturi slide. By being located on the beveled edge, the opening of the auxiliary hole is effectively kept out of the high velocity low air pressure air stream at low air velocities during partial throttle conditions. The auxiliary hole bleeds vacuum from the interior of the variable Venturi slide, picked up by the other lift hole located on the bottom of the slide, and slows the slide lift rate. The slide stays down or rises very slowly under conditions in which a conventional prior art slide would be starting to rise at a linear rate. At higher air velocities, when the throttle plate is opened quickly or operated at near wide open conditions, the opening of the auxiliary hole adds a vacuum to the interior of the slide, and increases the slide lift rate. In such manner, the lift rate of the slide is reduced at lower air pressure and velocity, while at the same time, the lift rate of the slide is increased at higher air pressure and velocity. The resulting non-linear lift rate keeps the fuel mixture lean under partial throttle conditions when driving conditions require it, yet provides a ratio of air to fuel mixture that represents the optimum value for the prevailing conditions of engine speed and load throughout a broad range, thereby effecting an improvement in fuel economy and reducing the emission of pollutants.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
In any internal combustion engine using a mechanical or electronic throttle system, it is possible to open the throttle fast enough to cause the air velocity in the intake manifold to drop momentarily to an undesirably small value. This low value of air velocity, passing through the throttle body, has a detrimental affect on fuel distribution and can promote increased wetting of the walls in the region of the throttle body and intake manifold. Conversely, the throttle can also be closed too quickly for proper transient fuel control. In this latter case, it is desirable to keep the manifold air velocity below a certain upper limit.
Certain carburetors, which are known to those skilled in the art, are constant velocity type carburetors which control air velocity with a mechanical means via the use of a diaphragm controlled plunger throttling valve. These types of constant velocity (CV) carburetors are in common use on certain motorcycles and are said to improve throttle response when compared to non-constant velocity carburetors. The Suzuki Corporation, on several models of motorcycles, utilizes a twin throttle mechanism. The primary throttle is mechanically actuated and connected to the handlebar twist grip by a cable. The secondary throttle is controlled electronically and can be used to limit the effective opening rate of the primary throttle. This arrangement generally allows the two throttles to keep throttle air velocity above some lower limit. However, this type of twin throttle mechanism does not always maintain the air velocity below an upper limit.
It would therefore be significantly beneficial if a control system could be provided for an internal combustion engine which controls the physical position of a throttle plate, in the throttle body structure, as a dual function of both a manually provided throttle control signal and the velocity of air passing through the throttle body. It would also be significantly beneficial if the velocity passing through a throttle could be maintained between an upper and lower velocity limit under all conditions, even when sudden changes are requested by the operator of the internal combustion engine.
A method for controlling the operation of an engine, made in accordance with the present invention, comprises the steps of receiving a throttle command signal and determining a commanded throttle position as a function of the manually caused throttle command signal. The present invention further comprises the steps of determining a mass air flow through a preselected portion of an air intake conduit of the engine and determining a density of air passing through the preselected portion of the air intake conduit of the engine. The present invention comprises the steps of determining an effective area of the preselected portion of the air intake conduit and also determining an air flow velocity through the preselected portion of the air intake conduit. In a particularly preferred embodiment of the present invention, the preselected portion of the air intake conduit is the throttle body and air conducting regions nearby. The present invention further comprises the steps of comparing the air flow velocity to an acceptable range of velocities and providing an amended throttle command signal in response to the air flow velocity not being within the acceptable range of velocities. In other words, if the commanded throttle position causes the air flow velocity through the throttle body region to fall outside an acceptable velocity range, the commanded throttle position is replaced by an amended throttle command signal in order to cause the air velocity to change sufficiently to be within the acceptable range.
In certain embodiments of the present invention, the commanded throttle position is a percentage of full travel of the throttle relative to a throttle body structure. The mass air flow determining step can comprise the step of measuring the mass air flow directly with the mass air flow sensor or, alternatively, it can comprise the step of calculating the mass air flow as a function of barometric pressure, manifold pressure, temperature, and effective area of the preselected portion of the air intake conduit. The air density determining step can comprise the steps of measuring a temperature at the throttle body, measuring a pressure at the throttle body, and calculating the air density as a function of pressure and temperature.
The present invention can further comprise the step of determining the effective area by selecting the effective area from a table of a plurality of magnitudes of effective areas stored as a function of an associated plurality of throttle positions. The use of a look-up table of this type simplifies the procedure of rapidly determining an effective throttle area as a function of the angular position, expressed as a percentage of full travel, of the throttle plate within the throttle body structure. The airflow velocity determining step of the present invention can comprise the step of calculating the air flow velocity as a function of the mass air flow through the throttle body, the density of air passing through the throttle body, and the temperature of air within the air manifold of the engine. The throttle command signal receiving step of the present invention can comprise the step of receiving a signal which represents the position of a manually movable throttle control handle.
More simply stated, the method of controlling the operation of an engine, in accordance with the present invention, comprises the steps of receiving a throttle command signal and causing a throttle plate to move to a position determined as the dual function of both the throttle command position and an air velocity through the throttle body.